Method and system for spectral examination of vascular walls through blood during cardiac motion

Abstract

A method for improving the treatment and / or examination of vessel walls through fluid, such as blood, functions by identifying the points in time when the catheter is closest to the vessel wall or farthest from the vessel wall. Identification of this relative location enables improved spectral readings in larger vessels. In short, instead of trying to overcome motion (e.g., by centering the catheter), this approach takes advantage of motion by identify times when the catheter is closer to the vessel wall, in order to gather more useful spectral information or improve the efficacy of the treatment of the vessel walls. In the specific example, the invention is used for near infrared (NIR) spectroscopy. In some embodiments, the catheter head is designed to induce relative movement between the head and the vessel walls.

Description

BACKGROUND OF THE INVENTION[0001]Probe-based, such as catheter-based, optical systems are applicable to a number of diagnostic and therapeutic medical applications. Optical coherence tomography is used to provide spatial resolution, enabling the imaging of internal structures. Spectroscopy is used to characterize the composition of structures, enabling the diagnosis of medical conditions, by differentiating between cancerous, dysplastic, and normal tissue structures, for example. Ablation systems are used to remove or destroy structures within the body to address various diseases, such as tachycardias, tumors, and coronary artery disease, in another example of a probe-based optical system.[0002]For example, in one specific spectroscopic application, an optical source, such as a tunable laser, is used to access or scan a spectral band of interest, such as a scan band in the near infrared or 750 nanometers (nm) to 2.5 micrometers (μm). The generated light is used to illuminate tissue ...

AI Technical Summary

Benefits of technology

[0009]One approach to addressing the influence of motion is electrocardiographic gating (ECG gating), where some pre-selected segment of the cardiac cycle is used for taking measurements. ECG gating can enable spectral acquisition during a period of lesser movement, or may reduce the variance in the distance between the vessel and the catheter head between samples by collecting information at the some specified point in the cycle over multiple cardiac cycles. ECG gating, however, has had limited success due to the weak correlation between vessel motion and catheter motion.

[0011]The present invention concerns an approach for improving the treatment and / or examination of vessels walls through fluid, such as blood. In the specific example, the invention is used for near infrared (NIR) spectroscopy. The invention can take advantage of the probe, such as catheter head, motion by identifying the points in time when the head is closest to the vessel wall or farthest from the vessel wall. Identification of this relative location enables meaningful spectral readings in larger vessels. In short, instead of trying to overcome motion (e.g., by centering the catheter), this approach takes advantage of motion by identify times when the catheter is closer to the vessel wall, in order to gather more useful spectral information or improve the efficacy of the treatment of the vessel walls.

Problems solved by technology

The treatment and / or analysis of vessel walls through blood, however, are complicated further by the fact that the physical relationship between the probe, and typically the probe head, and the blood vessel walls is poorly controlled.

Thus, in diagnostic applications, such as spectroscopy applications, the unknown pathlength will affect the degree to which the detected spectrum is dominated by unwanted signal sources, such as blood, thus making it difficult to isolate the spectral response of the vessel walls or other structures of interest.

The problem is further complicated in large vessels since the catheter head can be so far from the vessel walls that it is impossible to acquire any useful information.

ECG gating, however, has had limited success due to the weak correlation between vessel motion and catheter motion.

These approaches are clinically undesirable, however.

Among other problems, this may cause all signals to be poor in a large vessel, due to the large catheter-to-vessel distance, however.

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